1. Field of the Invention
The present invention relates to an equalizer based receiver operation method and apparatus in a mobile communication system. More particularly, the present invention relates to a receiver operation method and apparatus for adaptively changing a position of a channel estimation tap and equalizer tap considering a delay profile of a multi path channel.
2. Description of the Related Art
In recent years, as mobile communication systems providing high-speed data transmission, such as a Wideband Code Division Multiple Access (WCDMA) system and a High Speed Downlink Packet Access (HSDPA) system, are being standardized and commercialized, research on an equalizer based receiver that is suitable for high speed reception is being actively conducted.
The conventional equalizer based receiver includes a multi-tap channel estimator having a tap that provides sufficient duration to receive a delay profile of a receive channel and an equalizer. A multi tap channel estimator having a tap of sufficient length as described above is a structure designed for a worst case scenario in which a delay profile of a multi path receive channel may be long but, in reality, the long delay profile does not always appear in every channel reception environment.
Accordingly, in the conventional art, a technique of selectively using a multi tap having a long length depending on a channel environment is provided. That is, a technique of estimating a delay profile of a receive signal depending on a multi path, locking only a necessary tap, among a plurality of taps, having a long length, unlocking remaining taps, and receiving a signal in a receiver is provided. The technique of locking and using only a necessary tap has an advantage of being capable of reducing power consumption by only using hardware when required by certain conditions and being capable of eliminating a performance loss appearing when locking a tap of no multi path energy.
However, the technique of selecting and using only one tap among a plurality of taps as described above has a fundamental disadvantage of still requiring a multi tap of sufficient length to ensure performance for all conditions. Also, because a receiver has a multi tap based on a fixed position, a delay profile of a multi path channel may be out of a multi tap range of the receiver due to a high speed movement of a Mobile Station (MS). Thus, there is a problem that performance may be lost. For example, in the case of the receiver selecting a tap based on a fixed position, after a time lapse, a position of a delay profile of a multi path channel may be out of a range of the selected tap and thus, the energy of a receive signal that is out of range is reduced and a corresponding performance loss occurs. The above performance loss can be addressed by designing a multi tap of a channel estimator with greater duration, but such a design causes a problem of increasing a size of hardware and complexity. Accordingly, there is a need to provide an improved equalizer based receiver operation method and apparatus in a mobile communication system.